This invention relates generally to the field of hard disc drive data storage devices, and more particularly, but not by way of limitation, to rotational support of disc drive actuators.
Disc drives of the type known as xe2x80x9cWinchesterxe2x80x9d disc drives, or hard disc drives, are well known in the industry. Such disc drives magnetically record digital data on a plurality of circular, concentric data tracks on the surfaces of one or more rigid discs. The discs are typically mounted for rotation on the hub of a brushless DC spindle motor. In disc drives of the current generation, the spindle motor rotates the discs at speeds of up to 15,000 RPM.
Data are recorded to and retrieved from the discs by an array of vertically aligned read/write head assemblies, or heads, which are controllably moved from track to track by an actuator assembly. The read/write head assemblies typically consist of an electromagnetic transducer carried on an air bearing slider. This slider acts in a cooperative pneumatic relationship with a thin layer of air dragged along by the spinning discs to fly the head assembly in a closely spaced relationship to the disc surface. In order to maintain the proper flying relationship between the head assemblies and the discs, the head assemblies are attached to and supported by flexures attached to the actuator.
The actuator assembly used to move the heads from track to track has assumed many forms historically, with most disc drives of the current generation incorporating an actuator of the type referred to as a rotary voice coil actuator. A typical rotary voice coil actuator consists of a pivot shaft fixedly attached to the disc drive housing base member closely adjacent the outer diameter of the discs. The pivot shaft is mounted such that its central axis is normal to the plane of rotation of the discs. The actuator is mounted to the pivot shaft by precision ball bearing assemblies within a bearing housing. The actuator supports a flat coil which is suspended in the magnetic field of an array of permanent magnets, which are fixedly mounted to the disc drive housing base member.
On the side of the actuator bearing housing opposite to the coil, the actuator assembly typically includes a plurality of vertically aligned, radially extending actuator head mounting arms, to which the head suspensions mentioned above are mounted. These actuator arms extend between the discs, where they support the head assemblies at their desired positions adjacent the disc surfaces. When controlled DC current is applied to the coil, a magnetic field is formed surrounding the coil which interacts with the magnetic field of the permanent magnets to rotate the actuator bearing housing, with the attached head suspensions and head assemblies, in accordance with the well-known Lorentz relationship. As the actuator bearing housing rotates, the heads are moved generally radially across the data tracks of the discs along an arcuate path.
In the past, disc drives were typically used for storage of data in personal computers and in storage arrays for storing huge amounts of data in enterprise applications. Presently, however, drives are being contemplated for use in a wide variety of consumer products, such as television set-top video recorders, video game consoles, and hand-held computers. These applications present a new set of challenges to the drive industry, requiring that drives be more quiet and smaller than ever before. In particular, there is a need to produce drives having a height which is decreased relative to that of conventional drives to enable use in hand-held and card-type applications.
A primary factor in limiting potential decreases in drive height is the actuator pivot. A typical pivot mechanism has two ball bearing assemblies having ball bearings which roll between inner and outer races, a stationary shaft attached to the inner races and a rotating sleeve attached to the outer races. The sleeve is typically secured within a bore in the actuator body and the stationary shaft typically is attached to the base deck and the top cover of the disc drive. The bearings are preloaded such that the inner races are forced toward one another. The inner and outer races of each bearing assembly are thereby slightly offset so as to take up radial clearances built into the bearing assemblies. Without preload, the sleeve would be more free to move along the pivot axis, to translate horizontally or to pivot about a horizontal axis, causing unwanted head movement. In addition, lack of preload would lead to unwanted vibrations, contributing to the likelihood of resonance within the actuator system. It is the provision of two bearing assemblies which allows preload. However, one disadvantage of this arrangement is that absolute minimum drive height is limited by the combined height of the two bearing assemblies in addition to the vertical spacing between them.
What the prior art has been lacking is a low profile actuator pivot assembly which is easily assembled, inexpensive and which exhibits adequate stiffness to prevent excess vibration of the actuator assembly.
The present invention is directed to a low-profile actuator pivot bearing assembly. The assembly includes two generally coaxial bearings having differing diameters so as to define inner and outer bearings. This arrangement permits the pivot assembly to be constructed with a lower profile than conventional pivot bearings. These and other and benefits will become apparent upon a review of the attached figures and the accompanying description.